Hand and Upper Extremity Surgery
Principles of Hand Surgery
Candidates must understand hand anatomy (flexor and extensor zones, nerve territories), tendon injuries, nerve injuries, fractures (scaphoid, distal radius, phalanges), infections (paronychia, felon, tenosynovitis), and compressive neuropathies (carpal tunnel, cubital tunnel).
Key Concepts
- Flexor tendon zones: Zone I (FDS insertion to fingertip), II (no man's land, FDS insertion to A1 pulley), III (palm), IV (carpal tunnel), V (forearm). Repair with core suture and epitendinous repair; early mobilization.
- Extensor tendon zones: Even zones (over bones) and odd zones (over joints). Mallet finger (zone I), boutonnière deformity (zone III).
- Nerve injuries: Median nerve (thenar atrophy, thumb opposition weakness), ulnar nerve (clawing, Froment's sign), radial nerve (wrist drop). Repair with tension-free coaptation; nerve grafting for gaps.
- Scaphoid fracture: Most common carpal fracture; risk of nonunion and AVN. Snuffbox tenderness; MRI most sensitive. Treatment: cast for nondisplaced; screw fixation for displaced or proximal pole.
- Distal radius fracture: Colles' (dorsal angulation), Smith's (volar angulation). Treatment: cast for stable; surgery for unstable (volar locking plate).
- Infections: Paronychia (incision and drainage), felon (I&D), tenosynovitis (Kanavel's signs: finger held in flexion, fusiform swelling, tenderness along sheath, pain with passive extension).
Traps
- Flexor tendon zone II: Historically poor results; now with modern techniques, repair and early mobilization yield good outcomes.
- Scaphoid fracture: May not be visible on initial X-ray; treat as fracture if snuffbox tenderness and immobilize.
- Carpal tunnel syndrome: Electrodiagnostic studies confirm; surgery (release) for severe or failed conservative.
- Kanavel's signs: All four signs may not be present; high index of suspicion.
Worked Example
A 30-year-old male sustains a volar wrist laceration with inability to flex the index finger at the PIP and DIP joints. Diagnosis: flexor tendon injury in zone II. Rule of thumb: Zone II flexor tendon repair requires careful technique with core suture and early controlled mobilization to prevent adhesions. Refer to hand surgery.